This invention relates to the lining of pipelines or existing conduits using flexible tubular materials which are impregnated with curable synthetic resins, and more particularly to a lateral seal for sealing the junction between the conduit being relined and a lateral connection.
The most widely practiced method of lining existing pipelines and conduits using a flexible resin impregnated lining or "cured in place pipe" is the Insituform.RTM. Process and is described in U.S. Pat. No. 4,009,063 and No. 4,064,211, the contents of which are incorporated herein by reference. Briefly, in the Insituform.RTM. Process, an elongated flexible tubular lining of a resin impregnable material, such as a needled felt, which has been impregnated with a thermosetting synthetic resin, is installed within an existing pipeline that is in need of repair. The impregnated liner may be pulled into the conduit by a rope or cable, and a fluid-impermeable inflation bladder or tube is then everted within the liner as described in detail in U.S. Pat. No. 4,009,063. Alternately, the liner is installed utilizing an eversion process as described in U.S. Pat. No. 4,064,211. The liners utilized in the Insituform.RTM. Process are flexible and generally have a smooth impermeable coating on one side. After inversion, this smooth layer becomes the inside of the liner.
After the flexible liner is positioned within the conduit, the liner is pressurized from within, preferably using a fluid such as water. The fluid pressure forces the liner radially outwardly to engage and conform to the interior surface of the existing pipeline. The resin is then cured by recirculating heated water to form a relatively hard, tight-fitting rigid pipe lining that effectively relines the existing pipeline. In addition to curing by heat, the resin can be cured using other forms of radiant energy, such as ultra violet light as described in U.S. Pat. No. 4,135,958 or visible light in U.S. Pat. No. 4,518,247 and U.S. Pat. No. 4,680,066, the contents of which are incorporated herein by reference. Alternatively, radiant energy in the form of electrical energy or sound waves can be used to initiate the cure. Once the liner is completely cured, lateral connections are cut to existing services to the liner by remote cutters, which are common expedients in the art.
There is a strong demand and a need to seal the connections between the main conduit and any lateral pipes, in addition to the repair of the main pipeline. This is an important consideration in the process of relining an entire existing sewer system in order to effectively prevent the ingress of ground water into the system and outflow of effluent from the system.
In a typical municipal sewer system, there are a plurality of lateral pipeline entering a main conduit between adjacent manhole access points. The time needed to cure a cured in place liner that has been installed in a main pipeline is typically between four and six hours. Using existing methods of lining or lateral pipelines or is not possible to perform any significant repair or lining operations of the plurality of lateral connections at the same time that a main conduit is being lined. Repair or sealing of each lateral connection using conventional lining methods is difficult. Such long cure times would generally increase the amount of time required to complete the repair of a particular line by almost a full day of work for each lateral connection. Since a typical residential street may have about ten or more homes between manholes, this would increase the operating time needed to complete the lining operation for repair of the main pipeline between adjacent manholes from one day to ten days or more.
There are presently several proposals available for lining lateral pipelines and forming a seal at the lateral connection. Some of these call for lining the lateral from the outlet of the service lateral inward to the mainline conduit. One such method is described in U.S. Pat. No. 5,108,533. Others utilize a launcher-type apparatus that inserts a lining from the main pipeline into the lateral connection at a location remote from the access to the main pipeline. This process is described in U.S. Pat. No. 5,624,629, the contents of which are incorporated herein by reference. Here, a second or subsequent lateral is lined and cured, at the same time as an initial lateral is being lined in an effort to reduce the overall time of repair of the system. However, because several laterals are typically connected to a particular mainline conduit, it is difficult and almost physically impossible to install lateral seals at more than one location within a mainline conduit at the same time.
Accordingly, it is desirable to provide an improved cured in place lateral seal for lining the connection of a lateral to a main pipeline which overcomes the serious time deficiencies of the prior art and provides an efficient seal. It is desirable to improve the speed and cycle time required to install a lateral seal in order to provide a truly cost effective service of installation of lateral seals.